BICYCLE PROPULSION

Abstract

Bicycle drive unit (40, 70) supporting a crankshaft (42) of a bicycle (10), the bicycle drive unit (40, 70) comprising: a motor (44) configured to assist the propulsion of the bicycle (10); a housing (46, 76) in which the motor (44) is at least partially housed and which is / will be attached to a frame of the bicycle (10); and a vibration modification section (48, 78) formed from a material different from a material of the housing (46, 76), wherein the vibration modification section (48, 78) is provided in an inner cavity of the housing (46, 76) for modifying at least one vibration transmitted by a vibration characteristic of the housing (46, 76) and to the housing (46, 76), wherein the vibration modification section (48, 78) is at least partially attached to an inner surface of the housing (46, 76).

Description

PRIOR ARTThe present invention relates to a bicycle drive unit.Japanese Laid-Open Patent Publication No. JP 2015-209159 A discloses a bicycle drive unit provided near a crankshaft of a bicycle and having a motor that assists the advancement of the bicycle.JP 2016-112 928 A discloses a drive unit mounted on an electric bicycle. The drive unit mounted on an electric bicycle includes a motor, a drive shaft rotated by the driving force of the motor, a first member fixed to the outer circumferential surface of the drive shaft to be rotated together with the drive shaft, a sprocket attached to one end of the drive shaft and transmitting the driving force of the motor to a wound chain, and an annular damper attached to the drive shaft and positioned between the sprocket and the first member.JP H09-95 290 A discloses a shrink-packed battery pack. The shrink-wrapped battery pack is electrically connected to an inner box having a grip portion in the state where the battery pack is accommodated in the inner box.JP 2015-209 159A discloses a shift control device including a shift control part. The shift control part selects a usable shift range for the operation modes and controls the electric switching unit in the selected shift range.DE 600 15 469 T2 shows a motor-assisted drive unit for a motor-assisted vehicle comprising a motor accommodated in a housing as an auxiliary power source, the motor-assisted drive unit comprising: a first switchboard and a second switchboard on which control / regulation devices of the motor are mounted, respectively; wherein the first and second switchboards are arranged in the housing in such a manner that they extend in the direction perpendicular to a motor shaft of the motor; wherein the second switchboard overlaps with a part of the first switchboard as viewed in the axial direction of the motor; wherein the first switchboard has a hole centered on the motor shaft for inserting the motor shaft; and wherein the second switch panel has a first area that overlaps with the motor, characterized in that the second switch panel has a second area that does not overlap with the motor, the first area being smaller than the second area.DE 60 2005 001 513 T2 discloses a bicycle driving force transmission mechanism having a chain alignment structure, wherein the bicycle driving force transmission mechanism comprises a rear wheel and a rear wheel driving gear, a driven gear formed on the rear wheel, and an endless driving chain, wherein a driving gear of a driving gear body is rotatably driven by a crankshaft, the endless driving chain is wound around the rear wheel driving gear and the driven gear, and wherein the chain alignment structure comprises a chain guide member, characterized in that an endless transmission chain extends between and is wound around the driving gear body and a transmission gear body, that the transmission gear body is mounted on an output shaft, and the rear wheel driving gear is fitted on the output shaft to be constantly rotated in a manner with the output shaft, the chain guide member is disposed on a winding side of the endless transmission chain from the drive sprocket, the driven sprocket is drivingly connected to the output shaft rotated in an engaged manner with the rear wheel of a bicycle, wherein the power of the output shaft is transmitted to the rear wheel via the path of the rear wheel drive sprocket, the endless drive chain, and the driven sprocket, wherein the driven sprocket is configured to be always rotated in one with the output shaft, and a one-way clutch transmitting the rotation in the normal direction of the crankshaft to the drive sprocket is disposed between the crankshaft and the drive sprocket.The post-published document KR 10 2018 093 340 A shows an electric bicycle comprising: a wheel; a motor applying a rotational force to the wheel; a battery supplying power to the motor; a generator for storing energy of the battery; and a pedal for driving the generator. In addition, the generator may include: a transmission unit for increasing a rotational force of the pedal; a generator that generates power using the rotational force of the transmission unit; and a sound reflecting member that reflects sound generated by the generator to the transmission unit.SUMMARY OF THE INVENTIONIn a case where the motor of the above bicycle drive unit is driven and a housing vibrates, an elastic vibration wave is generated by the vibration of the housing and is output from / from the housing. The elastic vibration wave output from the housing may cause the user to feel inconveniences depending on the frequency or intensity. Thus, user-friendliness can be reduced.It is an object of the present invention to provide a bicycle drive unit that contributes to improvement of user-friendliness.According to a first aspect of the present invention, a bicycle drive unit that supports a crankshaft of a bicycle includes a motor configured to assist the propulsion of the bicycle, a housing in which the motor is / is at least partially accommodated and which is fixed to a frame of the bicycle, and a vibration changing portion formed of a material different from a material of the housing. The vibration changing portion is provided in an inner cavity of the housing for changing at least one of a vibration characteristic of the housing and vibration transmitted to the housing. The vibration changing portion is at least partially attached to an inner surface of the housing.In the bicycle drive unit according to the first aspect, at least one of the frequency and intensity of an elastic vibration wave output from the housing is changed, so that the user hardly experiences any inconvenience. This contributes to improvement of user-friendliness.In accordance with a second aspect of the present invention, the bicycle drive unit according to the first aspect is configured so that the vibration changing portion reduces a level of the sound pressure output from the housing by performing at least one of a reduction in the intensity of the vibration of the housing and a reduction in the intensity of the vibration transmitted to the housing.With the bicycle drive unit according to the second aspect, the intensity of an elastic vibration wave output from the housing is changed, so that the user hardly experiences any inconvenience.In accordance with a third aspect of the present invention, the bicycle drive unit according to the first or second aspect is configured so that the vibration changing portion includes an elastic member.In the bicycle drive unit according to the third aspect, the elastic member suitably changes the frequency and the intensity of an elastic vibration wave output from the housing.In accordance with a fourth aspect of the present invention, the bicycle drive unit according to the third aspect is configured so that the elastic member includes at least one of a rubber material, a foamed material, a fiber material, and a spring.In the bicycle drive unit according to the fourth aspect, at least one of the frequency and the intensity of an elastic vibration wave output from the housing is suitably changed by at least one of the rubber material, the foamed material, the fiber material, and the spring.In accordance with a fifth aspect of the present invention, the bicycle drive unit according to any one of the first to fourth aspects is configured so that the vibration changing portion is sheet-shaped.In the bicycle drive unit according to the fifth aspect, the vibration changing portion limits the enlargement of the bicycle drive unit.The vibration changing portion at least partially attached to an inner surface of the housing performs at least one of damping vibration of the housing and absorbing an elastic vibration wave between the vibration source and the housing. Thus, an elastic vibration wave output from the housing is reduced. In addition, the vibration changing portion is stably attached to the bicycle drive unit.In accordance with a seventh aspect of the present invention, the bicycle drive unit according to the sixth aspect is configured such that the housing includes a first housing and a second housing, and the vibration changing portion is at least partially attached to an inner surface of the first housing.In the bicycle drive unit according to the seventh aspect, the vibration changing portion performs damping of vibration of the first housing and / or absorption of an elastic vibration wave between the vibration source and the first housing.In accordance with an eighth aspect of the present invention, the bicycle drive unit according to the seventh aspect is configured so that the motor is supported by the second housing.Substantially, a thicker case reduces the vibration of the case and an elastic vibration wave output from the case. Accordingly, the housing is heavier. With the bicycle drive unit according to the eighth aspect, at least one of damping vibration of the first housing and absorption of an elastic vibration wave between the vibration source and the first housing can be performed while reducing the weight of the first housing that does not support the motor.In accordance with a ninth aspect of the present invention, the bicycle drive unit according to any one of the first to eighth aspects is configured so that the vibration changing portion is attached to a member accommodated at least partially in the inner cavity of the housing.In the bicycle drive unit according to the ninth aspect, the vibration changing portion absorbs an elastic vibration wave between the vibration source and the housing. In addition, the vibration changing portion is stably attached to the bicycle drive unit.In accordance with a tenth aspect of the present invention, the bicycle drive unit according to any one of the first to ninth aspects further includes a speed reduction mechanism that is provided in the inner cavity of the housing and reduces the rotational speed of an output shaft of the motor and outputs the rotation.In the bicycle drive unit according to the tenth aspect, in the bicycle drive unit including the speed reduction mechanism, at least one of the frequency and intensity of an elastic vibration wave output from the housing is changed so that the user hardly experiences any inconveniences.In accordance with an eleventh aspect of the present invention, the bicycle drive unit according to the tenth aspect is configured so that the speed reduction mechanism includes a plurality of gears.With the bicycle drive unit according to the eleventh aspect, the plurality of gears simplify the structure of the speed reduction mechanism.In accordance with a twelfth aspect of the present invention, the bicycle drive unit according to any one of the first to eleventh aspects further comprises the / a crankshaft.In the bicycle drive unit according to the twelfth aspect, in the bicycle drive unit provided around the crankshaft, at least one of the frequency and intensity of an elastic vibration wave output from the housing is changed, so that the user hardly experiences any inconvenience.The bicycle drive unit of the present invention contributes to improvement of user-friendliness.According to another aspect of the present invention, a bicycle drive unit that supports a crankshaft of a bicycle includes a motor configured to assist propulsion of the bicycle, a housing in which the motor is / is at least partially accommodated and which is mounted on a frame of the bicycle; and a vibration changing portion formed of a material different from a material of the housing, the vibration changing portion being provided in an inner cavity of the housing, for changing at least one of a vibration characteristic of the housing and vibration transmitted to the housing, the vibration changing portion being sheet-shaped.BRIEF DESCRIPTION OF THE DRAWINGSFIG. 1 is a side view of a bicycle including a first embodiment of a bicycle drive unit. FIG. 2 is a perspective view of the bicycle drive unit shown in FIG. 1. FIG. 3 is a plan view of the bicycle drive unit shown in FIG. 2. FIG. 4 is a plan view of an inner surface of a first housing shown in FIG. 2. FIG. 5 is a cross-sectional view taken along line 5- 5 in FIG. 3. FIG. 6 is a perspective view showing a second embodiment of a bicycle drive unit. FIG. 7 is a plan view of the bicycle drive unit shown in FIG. 6. FIG. 8 is a plan view of an inner surface of a first housing shown in FIG. 6. FIG. 9 is a cross-sectional view taken along line 9-9 in FIG. 7. FIG. 10 is a cross-sectional view of a modified example of a bicycle drive unit.EMBODIMENTS OF THE INVENTIONFirst EmbodimentA bicycle 10 having a first embodiment of a bicycle drive unit 40 will now be described with reference to FIGS. 1 to 5. The bicycle 10 may be a mountain bike, a race bike, or a city bike.As shown in FIG. 1, the bicycle 10 includes a bicycle body 12, wheels 14, a drive mechanism 16, a battery 18, and the bicycle drive unit 40.The bicycle body 12 includes a frame 22, a front fork 24 connected to the frame 22, and a handlebar 26B connected to the front fork 24 and attachable to and detachable from the front fork 24 via a shaft 26A. The front fork 24 is supported by the frame 22.The wheels 14 include a front wheel 28 and a rear wheel 30. the front wheel 28 includes an axle 28A connected to an end of the front fork 24. The rear wheel 30 includes an axle 30A connected to a rear end 22A of the frame 22.The drive mechanism 16 includes a crank 32 and pedals 34. the crank 32 includes a crankshaft 42 and crank arms 32A. The drive mechanism 16 transmits the human driving force acting on the pedals 34 to the rear wheel 30. the drive mechanism 16 includes a front rotating body 36 connected to an output portion 52 of a drive unit 40. The front rotating body 36 includes a sprocket, a pulley, or a bevel gear. The drive mechanism 16 is configured to transmit rotation of the crank 32 to a rear rotating body 38 connected to the rear wheel 30 via, for example, a chain, a belt, or a shaft. The rear rotating body 38 includes a sprocket, a pulley, or a bevel gear. A one-way clutch (not shown) is provided between the rear rotating body 38 and the rear wheel 30. The one-way clutch is configured to allow forward rotation of the rear wheel 30 in a case where the rear rotating body 38 is rotated in forward rotation, and prevent rearward rotation of the rear rotating body 38 in a case where the rear wheel 30 is rotated rearward. The front rotating body 36 may include a plurality of front sprockets. The rear rotating body 38 may include a plurality of rear sprockets.The battery 18 includes a battery unit 18A having one or more battery cells and a battery holder 18B supporting the battery unit 18A. A battery cell includes a rechargeable cell. The battery 18 is mounted on the bicycle 10 to supply electric power to other electrical components electrically connected to the battery 18 via wires, such as the bicycle drive unit 40. The battery 18 may be mounted on the outside of the frame 22 or at least partially housed in the frame 22.As shown in FIGS. 2 and 5, the bicycle drive unit 40 supports the crankshaft 42 of the bicycle 10. the bicycle drive unit 40 includes an engine 44, a housing 46, and a vibration changing portion 48. the bicycle drive unit 40 further includes the crankshaft 42, a speed reduction mechanism 50, the output portion 52, bearings 54, a first one-way clutch 56, a second one-way clutch 58, and a controller 60. the bearings 54 include a first bearing 54A, a second bearing 54B, a third bearing 54C, and a fourth bearing 54D.The motor 44 is configured to assist in the advancement of the bicycle 10. The motor 44 includes an electric motor. The motor 44 is a so-called brushless motor. The motor 44 is provided to transmit rotation to a human driving force transmission path extending from the pedals 34 to the rear wheel 30 shown in FIG. 1. The engine 44 is connected to the human driving force transmission path between the crankshaft 42 and the front rotating body 36. The controller 60 shown in FIG. 5 includes a board and a driving circuit. The driving circuit includes an inverter circuit and controls electric power supplied from the battery 18 shown in FIG. 1 to the motor 44.As shown in FIG. 2, the housing 46 at least partially receives the motor 44 and is connected to the frame 22 of the bicycle 10.The housing 46 includes a first housing 62 and a second housing 64. the housing 46 further includes coupling portions 66 that connect the bicycle drive unit 40 to the frame 22. The coupling portions 66 are provided on an outer periphery of the housing 46. The coupling portions 66 protrude from the outer periphery of the housing 46. The coupling portions 66 include holes 66A into which the bolts (not shown) are / are inserted to fix the bicycle drive unit 40 to the frame 22.As shown in FIG. 3, the first housing 62 covers one end side of the bicycle drive unit 40 with respect to a width direction of the bicycle 10. The first housing 62 and the second housing 64 are fastened together by screws 46A.As shown in FIGS. 4 and 5, the first housing 62 includes a first hole 62A. An axial end of the crankshaft 42 is inserted into the first hole 62A. The first bearing 54A is provided between the first hole 62A and the crankshaft 42. The first housing 62 supports the crankshaft 42 via the first bearing 54A such that the crankshaft 42 is rotatable with respect to the first housing 62.As shown in FIG. 5, the second housing 64 includes a second hole 64A and a third hole 64B. The other axial end of the crankshaft 42 and the output portion 52 are inserted into the second hole 64A. The second bearing 54B is provided between the second hole 64A and the output portion 52. The second housing 64 supports the output portion 52 via the second bearing 54B such that the output portion 52 is rotatable with respect to the second housing 64. A housing 44B of the motor 44 is fitted into the third hole 64B. The motor 44 is supported by the second housing 64. It is preferred that the second housing 64 is heavier than the first housing 62, and it is preferred that the first housing 62 and the second housing 64 comprise an aluminum material. In one example, the aluminum material comprises ADC 12. The first housing 62 and the second housing 64 may include a magnesium alloy or a resin material.The speed reduction mechanism 50 is provided in an inner cavity of the housing 46. The speed reduction mechanism 50 reduces the rotational speed of an output shaft 44A of the motor 44. the speed reduction mechanism 50 connects the motor 44 and the output portion 52. the speed reduction mechanism 50 reduces the rotational speed of the motor 44 and transmits the rotation to the output portion 52. the speed reduction mechanism 50 includes a plurality of gears 68. the plurality of gears 68 include a first gear 68A, a second gear 68B, a third gear 68C, and a fourth gear 68D. The speed reduction mechanism 50 further includes a rotation shaft 70.The rotary shaft 70 extends in parallel to the output shaft 44A of the engine 44 and the crankshaft 42. The third bearing 54C is provided between the rotation shaft 70 and the first housing 62. The first housing 62 rotatably supports the rotation shaft 70 via the third bearing 54C. The other axial end of the rotating shaft 70 is supported by the housing 44B of the motor 44. The fourth bearing 54D is provided between the rotation shaft 70 and the housing 44B. The housing 44B of the motor 44 rotatably supports the rotation shaft 70 via the fourth bearing 54D.The first gear 68A is provided on an outer periphery of the output shaft 44A of the motor 44. In one example, the first gear 68A is integrally formed with the output shaft 44A. Alternatively, the first gear 68A may be formed separately from the output shaft 44A and connected to the output shaft 44A.The second gear 68B is provided on an outer periphery of the rotation shaft 70. The second gear 68B is meshed with the first gear 68A. The first one-way clutch 56 is provided between the second gear 68B and the rotation shaft 70. The first one-way clutch 56 transmits rotation input to the second gear 68B from the motor 44 to the rotation shaft 70, and does not transmit rotation input from the output portion 52 to the second gear 68B and the motor 44 to the rotation shaft 70.The third gear 68C is provided on the outer periphery of the rotation shaft 70 at a position different from the second gear 68B. The third gear 68C rotates integrally with the rotation shaft 70. Alternatively, the third gear 68C may be formed separately from the rotary shaft 70 and connected to the rotary shaft 70.The fourth gear 68D is provided on an outer periphery of the output portion 52. The fourth gear 68D rotates integrally with the output portion 52. The fourth gear 68D is connected to the crankshaft 42 via the second one-way clutch 58. The second one-way clutch 58 transmits the rotation of the crankshaft 42 to the fourth gear 68D and does not transmit the rotation of the output portion 52 to the crankshaft 42.The first gear 68A has fewer teeth than the second gear 68B. The third gear 68C has fewer teeth than the fourth gear 68D. Thus, the rotational speed of the motor 44 is decreased in two steps by the gears 68A to 68D, and the rotation is transmitted to the output portion 52.The vibration changing portion 48 changes at least one of a vibration characteristic of the housing 46 or a vibration transmitted from a vibration source provided in the housing 46 to the housing 46. The vibration characteristic has a vibration frequency. The vibration source includes at least one of the motor 44, a rotating body provided in the housing 46, and a support member that supports a component provided in the housing 46. The vibration changing portion 48 includes a member different from the components necessary for the operation of the bicycle drive component 40. The components necessary for the operation of the bicycle drive unit 40 include, for example, the crankshaft 42, the engine 44, the speed reduction mechanism 50, the output portion 52, and grease applied to these components. The vibration changing portion 48 reduces the level of sound pressure output from the housing 46 by performing at least one of a reduction in the intensity of vibration of the housing 46 and a reduction in the intensity of vibration transmitted to the housing 46.The vibration changing portion 48 and the housing 46 are formed of different materials. The vibration changing portion 48 includes an elastic member. The elastic member includes at least one of a rubber material, a foamed material, a fiber material, and a spring. An example of the rubber material includes at least one of butyl rubber, natural rubber, and the like. An example of the foamed material includes a urethane elastomer. An example of the fiber material includes a polyester fiber. The spring comprises a machine element which is configured to be elastically deformed by vibrations transmitted to the housing 46 or to the inside of the housing 46. An example of the spring includes at least one of butyl rubber, natural rubber, and the like. In the example shown in FIG. 4, the vibration changing portion 48 is sheet-shaped. The shape of the vibration changing portion 48 is not limited to the shape of a sheet, and may have various shapes.The vibration changing portion 48 is provided in the inner cavity of the housing 46. The vibration changing portion 48 is at least partially attached to an inner surface of the housing 46. For example, the vibration changing portion 48 is attached to the inner surface of the first housing 62. The vibration changing portion 48 is provided at a portion of the first housing 62 corresponding to the motor 44. It is preferable that the vibration changing portion 48 is provided in a position of the housing 46 where the switching pressure level of the noise generated by the drive of the motor 44 and outputted from the housing 46 is easily reduced. The vibration changing portion 48 is fixed to the housing 46 by bonding or welding. It is preferable that the vibration changing portion 48 is fixedly attached to the inner surface of the housing 46.The operation of the bicycle drive unit 40 will now be described.The vibration changing portion 48 reduces the level of the sound pressure output from the housing 46. In a case where the vibration changing portion 48 includes a foamed material or a fiber material, the level of sound pressure output from the housing 46 is suitably reduced by absorption of the elastic vibration wave. In a case where the vibration changing portion 48 includes a rubber material, a foamed material, or a spring, the level of sound pressure output from the housing 46 is suitably reduced by reducing the vibration of the housing 46 or the vibration transmitted from the housing 46 or lowering the vibration frequency.Second EmbodimentA second embodiment of a bicycle drive unit 72 will now be described with reference to FIGS. 6 to 9. The bicycle drive unit 72 of the second embodiment is different from the bicycle drive unit 40 of the first embodiment in the form of a housing 76 and the structure of a speed reduction mechanism 80, but is otherwise the same as the bicycle drive unit 40 of the first embodiment. The same reference numerals are given to those components that are the same as the corresponding elements of the first embodiment. Such components will not be described in detail.As shown in FIGS. 6 and 9, the bicycle drive unit 72 supports the crankshaft 42 of the bicycle 10. the bicycle drive unit 72 includes the motor 44, the housing 76, and a vibration changing portion 78. the bicycle drive unit 72 further includes the crankshaft 42, the speed reducing mechanism 80, the output portion 52, bearings 74, a first one-way clutch 94, a second one-way clutch 96, and the controller 60. the bearings 74 include a first bearing 74A, a second bearing 74B, a third bearing 74C, a fourth bearing 74D, a fifth bearing 74E, and a sixth bearing 74F.As shown in FIG. 7, the housing 76 at least partially receives the motor 44 and is secured to the frame 22 of the bicycle 10.The housing 76 includes a first housing 82 and a second housing 84. the housing 76 further includes coupling portions 86 that connect the bicycle drive unit 72 to the frame 22. The coupling portions 86 are provided on an outer periphery of the housing 76. The coupling portions 86 protrude from the outer periphery of the housing 76. The coupling portions 86 include holes 86A into which bolts (not shown) are / are inserted to fix the bicycle drive unit 72 to the frame 22.As shown in FIG. 7, the first housing 82 is provided at a side of the bicycle drive unit 72 with respect to the width direction of the bicycle 10. As shown in FIG. 6, the second housing 84 is provided on the other side of the bicycle drive unit 72 with respect to the width direction of the bicycle 10. The first housing 82 and the second housing 84 are fastened together by bolts 76A.As shown in FIGS. 8 and 9, the first housing 82 includes a first hole 82A. An axial end of the crankshaft 42 is inserted through the first hole 82A. The first bearing 74A is provided in the first hole 82A. The first housing 82 supports the crankshaft 42 via the first bearing 74A such that the crankshaft 42 is rotatable with respect to the first housing 82.As shown in FIG. 9, the second housing 84 includes a second hole 84A and a third hole 84B. The other axial end of the crankshaft 42 and the output portion 52 are / are inserted through the second hole 84A. The second bearing 74B is provided in the second hole 84A. The second housing 84 supports the output portion 52 via the second bearing 74B such that the output portion 52 is rotatable with respect to the second housing 84. The housing 44B of the motor 44 is fitted into the third hole 84B. The motor 44 is supported by the second housing 84. It is preferred that the first housing 82 and the second housing 84 comprise an aluminum material. In one example, the aluminum material comprises ADC 12. Alternatively, the first housing 82 and the second housing 84 may include a magnesium alloy or a resin material. It is preferred that the second housing 84 is heavier than the first housing 82.The speed reduction mechanism 80 is provided in an inner cavity of the housing 76. The speed reduction mechanism 80 reduces the rotational speed of the output shaft 44A of the motor 44 and outputs the rotation. The speed reduction mechanism 80 connects the motor 44 and the output portion 52. the speed reduction mechanism 80 reduces the rotational speed of the output shaft 44A of the motor 44 and transmits the rotation to the output portion 52. the speed reduction mechanism 80 includes a plurality of gears 88. The plurality of gears 88 include a first gear 88A, a second gear 88B, a third gear 88C, a fourth gear 88D, a fifth gear 88E, and a sixth gear 88F. The speed reduction mechanism 80 further includes a first rotation shaft 90 and a second rotation shaft 92.The first rotation shaft 90 extends in parallel to the output shaft 44A of the engine 44 and the crankshaft 42. The third bearing 74C is provided between the first rotation shaft 90 and the first housing 82. The first housing 82 rotatably supports the first rotation shaft 90 via the third bearing 74C. The other axial end of the first rotation shaft 90 is supported by the housing 44B of the motor 44. The fourth bearing 74D is provided between the first rotation shaft 90 and the housing 44B. The housing 44B of the motor 44 rotatably supports the first rotation shaft 90 via the fourth bearing 74D.The second rotary shaft 92 extends in parallel to the output shaft 44A of the engine 44 and the crankshaft 42. The fifth bearing 74E is provided between the second rotation shaft 92 and the first housing 82. The first housing 82 rotatably supports the second rotation shaft 92 via the fifth bearing 74E. The other axial end of the second rotation shaft 92 is supported by the second housing 84. The sixth bearing 74F is provided between the second rotation shaft 92 and the second housing 84. The second housing 84 rotatably supports the second rotation shaft 92 via the sixth bearing 74F.The first gear 88A is provided on an outer periphery of the output shaft 44A of the motor 44. In one example, the first gear 88A is integrally formed with the output shaft 44A. Alternatively, the first gear 88A may be formed separately from the output shaft 44A and connected to the output shaft 44A.The second gear 88B is provided on an outer periphery of the first rotation shaft 90. The second gear 88B is meshed with the first gear 88A. The first one-way clutch 94 is provided between the second gear 88B and the first rotation shaft 90. The first one-way clutch 94 transmits rotation input to the second gear 88B from the motor 44 to the first rotation shaft 90 in a case where the crank 32 is rotated forward and does not transmit rotation transmitted to the first rotation shaft 90 from the output portion 52 to the second gear 88B and the motor 44 in a case where the crank 32 is rotated forward.The third gear 88C is provided on the outer periphery of the first rotary shaft 90 at a position different from the second gear 88B. The third gear 88C rotates integrally with the first rotation shaft 90. Alternatively, the third gear 88C may be formed separately from the first rotation shaft 90 and connected to the first rotation shaft 90.The fourth gear 88D is provided on an outer periphery of the second rotation shaft 92. The fourth gear 88D is meshed with the third gear 88C. The fourth gear 88D rotates integrally with the second rotation shaft 92 In one example, the fourth gear 88D is formed separately from the second rotation shaft 92 and connected to the second rotation shaft 92. Alternatively, the fourth gear 88D may be integrally formed with the second rotation shaft 92.The fifth gear 88E is provided on the outer periphery of the second rotary shaft 92 at a position different from the fourth gear 88D. The fifth gear 88E rotates integrally with the second rotation shaft 92 In one example, the fifth gear 88E is formed integrally with the second rotation shaft 92. Alternatively, the fifth gear 88E may be formed separately from the second rotation shaft 92 and connected to the second rotation shaft 92.The sixth gear 88F is provided on the outer periphery of the output portion 52. The sixth gear 88F rotates integrally with the output portion 52. The sixth gear 88F is connected to the crankshaft 42 via the second one-way clutch 96. The second one-way clutch 96 transmits the rotation of the crankshaft 42 to the sixth speed gear 88F and does not transmit the rotation of the output portion 52 to the crankshaft 42.The first gear 88A has fewer teeth than the second gear 88B. The third gear 88C has fewer teeth than the fourth gear 88D. The fifth gear 88E has fewer teeth than the sixth gear 88F. Thus, the rotational speed of the motor 44 is decreased in three steps by the gears 88A to 88F, and the rotation is transmitted to the output portion 52. A third one-way clutch may be provided between the second rotary shaft 92 and the fourth gear 88D or between the second rotary shaft 92 and the fifth gear 88E. The third one-way clutch transmits rotation transmitted from a side of the motor 44 to the output portion 52 in a case where the crank 32 is rotated forward, and does not transmit rotation transmitted from a side of the output portion 52 to the motor 44 in a case where the crank 32 is rotated forward. In a case where the third one-way clutch is provided, the first one-way clutch may be omitted.The vibration changing portion 78 changes at least one of a vibration characteristic of the housing 76 and a vibration transmitted to the housing 76 from a vibration source provided in the housing 76. The vibration characteristic includes a vibration frequency. The vibration source includes at least one of the motor 44, a rotating body provided in the housing 76, and a support member that supports a component provided in the housing 76. The vibration changing portion 78 includes a member different from the components required for the operation of the bicycle drive unit 72. The components required for operation of the bicycle drive unit 72 include, for example, the crankshaft 42, the engine 44, the speed reduction mechanism 80, the output portion 52, and grease applied to these components. The vibration changing portion 78 reduces the level of the sound pressure output from the housing 76 by performing at least one of a reduction in the intensity of the vibration of the housing 76 and a reduction in the intensity of the vibration transmitted to the housing 76.The vibration changing portion 78 and the housing 76 are formed of different materials. The vibration changing portion 78 includes an elastic member. The elastic member includes at least one of a rubber material, a foamed material, a fiber material, and a spring. An example of the rubber material includes at least one of butyl rubber, natural rubber, and the like. An example of the foamed material includes a urethane elastomer. An example of the fiber material includes a polyester fiber. The spring comprises a machine element which is configured to be elastically deformed by vibrations transmitted to the housing 46 or to the inside of the housing 46. The spring includes at least one of butyl rubber, natural rubber, and the like. In the example shown in FIG. 8, it is preferable that the vibration changing portion 78 is sheet-shaped. The shape of the vibration changing portion 78 is not limited to the shape of a sheet, and may have various shapes.The vibration changing portion 78 is provided in the inner cavity of the housing 76. The vibration changing portion 78 is at least partially attached to an inner surface of the housing 76. For example, the vibration changing portion 78 is attached to the inner surface of the first housing 82. The inner surface of the first housing 82 has a plurality of irregularities. The vibration changing portion 78 may include a plurality of blades 78A. The plurality of blades 78A are fixed to different portions of the inner surface of the first housing 82. It is preferable that the vibration changing portion 78 is provided in a portion of the housing 76 where the sound pressure level of the sound generated by the drive of the motor 44 and outputted from the housing 76 is easily reduced. The bicycle drive unit 72 of the second embodiment suitably reduces the level of sound pressure output from the housing 76 in the same operation as in the first embodiment. The vibration changing portion 78 is fixed to the housing 76 by bonding or welding. It is preferable that the vibration changing portion 78 is fixedly attached to the inner surface of the housing 76.Modified ExamplesThe foregoing description illustrates embodiments of a bicycle drive unit according to the present invention and is not intended to be limiting. The bicycle drive unit of the present invention includes, for example, the following modified examples of the above embodiments. Further, two or more of the modified examples may be combined. In the following modified examples, the same reference numerals are given to the components that are the same as the corresponding components of the embodiments. Such components will not be described in detail.The vibration changing portions 48, 78 of the embodiments may be / are attached to a member that is / is at least partially accommodated in the internal cavities of the housings 46, 76. The member accommodated in the inner cavities of the housings 46, 76 includes, for example, the crankshaft 42, the output portion 52, members constituting the speed reduction mechanisms 50, 80, and the board of the controller 60.FIG. 10 shows a modified example of the bicycle drive unit 40 of the first embodiment in which a vibration changing portion 98 is / is attached to the second gear 68B of the speed reduction mechanism 50. The vibration changing portion 98 is annular. The vibration changing portion 98 reduces the elastic vibration wave in the housing 46 by attenuating the vibration of the second gear 68B. Thus, the level of sound pressure output from the housing 46 is lowered.Grease holders may be provided around the gears 68, 88 of the speed reduction mechanisms 50, 80 in the internal cavities of the housings 46, 76 to apply grease to the gears 68, 88. The vibration changing portions 48, 78 may be / are fixed to the grease holders.The vibration changing portion 48 of the first embodiment may include a plurality of blades. The plurality of blades are attached to different portions of the inner surface of the first housing 62.The vibration changing portion 78 of the second embodiment may include only a single blade 78A. In this case, it is preferable that the blade 78A is attached to a portion of the first housing 82 where the sound pressure level is effectively reduced.The vibration changing portions 48, 78 of the embodiments may be provided at least partially in the second housings 64, 84. The vibration changing portions 48, 78 may be provided in both the first housings 62, 82 and the second housings 64, 84.The vibration changing portions 48, 78 of the embodiments may be integrally formed with the housings 46, 76. In this case, the housings 46, 76 and the vibration changing portions 48, 78 are insert-molded, for example.The vibration changing portions 48, 78 of the embodiments may be configured to change only the frequency of the vibration output from the housings 46, 76. The vibration changing portions 48, 78, for example, change an audible frequency of the vibration output from the housings 46, 76 to a frequency outside the range of the audible frequencies. In this case, the inconvenience experienced by the user can be reduced without reducing the sound pressure.A sound pressure reduction portion may be provided on the frame 22 to reduce the sound pressure of the vibration output from the housings 46, 76. The sound pressure reduction portion includes at least one of a rubber material, a foamed material, a fibrous material, and a spring. It is preferable that the sound pressure reduction portion is provided at a position contacting or close to the bicycle drive units 40, 72. The sound pressure reduction portion is provided, for example, on a down tube or seat tube of the frame 22.DESCRIPTION OF THE REFERENCE NUMERALS10 Bicycle; 40, 72 Bicycle drive unit; 42 Crankshaft; 44 Engine; 46, 76 Housing; 48, 78 Vibration changing portion; 50, 80 Speed reduction mechanism; 62, 82 First housing; 64, 84 Second housing; 68, 88 Transmission

Claims

A bicycle drive unit (40, 70) supporting a crankshaft (42) of a bicycle (10), the bicycle drive unit (40, 70) comprising: a motor (44) configured to assist propulsion of the bicycle (10); a housing (46, 76) in which the motor (44) is at least partially accommodated and which is / is attached to a frame of the bicycle (10); and a vibration changing portion (48, 78) formed of a material different from a material of the housing (46, 76), the vibration changing portion (48, 78) being provided in an inner cavity of the housing (46, 76), for changing at least one of a vibration property of the housing (46, 76) and transmitted to the housing (46, 76), the vibration changing portion (48, 78) being at least partially attached to an inner surface of the housing (46, 76).The bicycle drive unit (40, 70) according to claim 1, wherein the vibration changing portion (48, 78) reduces a level of the sound pressure output from the housing (46, 76) by performing at least one of a reduction in the intensity of the vibration of the housing (46, 76) and a reduction in the intensity of the vibration transmitted to the housing (46, 76).The bicycle drive unit (40, 70) according to claim 1 or 2, wherein the vibration changing portion (48, 78) has an elastic member, preferably an elastic member, comprising at least one of a rubber material, a foamed material, a fiber material, and a spring.The bicycle drive unit (40, 70) according to any one of claims 1 to 3, wherein the vibration changing portion (48, 78) is sheet-shaped.The bicycle drive unit (40, 70) according to any one of claims 1 to 4, wherein the housing (46, 76) comprises a first housing (62, 82) and a second housing (64, 84), and the vibration changing portion (48, 78) is at least partially attached to an inner surface of the first housing (62, 82), preferably the motor (44) is / is supported by the second housing (64, 84).The bicycle drive unit (40, 70) according to any one of claims 1 to 5, wherein the vibration changing portion (48, 78) is attached to a member at least partially accommodated in the inner cavity of the housing (46, 76).The bicycle drive unit (40, 70) according to any one of claims 1 to 6, further comprising a speed reduction mechanism (50, 80) that is provided in the inner cavity of the housing (46, 76) and reduces the rotational speed of an output shaft of the motor (44) and outputs the rotation, preferably the speed reduction mechanism (50, 80) comprises a plurality of gears (68, 88).The bicycle drive unit (40, 70) according to any one of claims 1 to 7, further comprising a crankshaft (42).A bicycle drive unit (40, 70) supporting a crankshaft (42) of a bicycle (10), the bicycle drive unit (40, 70) comprising: a motor (44) configured to assist propulsion of the bicycle (10); a housing (46, 76) in which the motor (44) is / is accommodated at least partially and which is attached to a frame of the bicycle (10); and a vibration changing portion (48, 78) formed of a material different from a material of the housing (46, 76), the vibration changing portion (48, 78) being provided in an inner cavity of the housing (46, 76), for changing at least one of a vibration property of the housing (46, 76) and transmitted to the housing (46, 76), the vibration changing portion (48, 78) being sheet-shaped.

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